SLOW map downloads - what IS the solution?

That's good to hear.

Now, try to find this GARMIN cable as there was something distinctively funny about it - can't remember what was it exactly but I myself did run into difficulties trying to update my previous unit (3590) on somebody else's PC and with generic USB cable and there was some sort of problem with this (like: maintaining device's power during upload as battery was heavily depleted? Really can't remember).

Needless to say I do use cable supplied by Garmin cable - it's connected to PC via my monitor's USB built-in hub.

Also, can you actually confirm - either with USB TreeView or via Device Manager and 'View -> Devices by Connection' that your nuvi definitely connects and is recognised by WIndows as USB2 device?

You could transfer some data from/to your nuvi and see what speeds you're getting?

I have 12 USB to mini-USB cables!  Not sure which one is the original Garmin cable (assuming I still have it).

There really is nothing special about mini-USB cables (I believe) as the USB connector typically has 4 wires (2 for power & 2 for data).  There is an option for a 5th wire, but this is tagged to ground to indicate "device presence" and (apparently) used by some devices for charging.  Some cables have a ferrite core loop on them to reduce RF pickup. There are some 8 pin mini-USB connectors used for video applications.

One of my cables is a little fatter than the others, black, and about 1 metre (3 feet) long, and has an "UP" designation on the mini-USB connector.  No other identifying marks.  Possibly this is the "real" Garmin cable?

I tested all my cables.  Only one did not cause the device to be connected to the computer (this was not the cable I was using).  The nuvi did NOT indicate it was connected, only that the battery was charging.  I presume this cable has only power connections (no data wires) and was for some device I obtained that did not have the ability or need for any data transfer.

All other cables allowed the nuvi to be connected and reported in USB Tree.

My nuvi 1350 appears in Device Manager 'View -> Devices by Connection' and reports "This device is working properly."

I can also see it in USB Tree Viewer:

      ========================== Summary =========================
Vendor ID                : 0x091E (Garmin International)
Product ID               : 0x23CC
USB Version              : 1.10
Port maximum Speed       : High-Speed (Companion Port 2-16 supports SuperSpeed)
Device maximum Speed     : Full-Speed
Device Connection Speed  : Full-Speed
Self powered             : no
Demanded Current         : 500 mA
Used Endpoints           : 3

<selected info below>
SupportedUsbProtocols    : 0x03
 Usb110                  : 1 (yes, port supports USB 1.1)
 Usb200                  : 1 (yes, port supports USB 2.0)
 Usb300                  : 0 (no, port not supports USB 3.0) -> but Companion Port 2-16 does

Child Device 1          : Garmin nuvi Flash USB Device (Disk drive) (Disk1)
Child Device 2          : Garmin nuvi SD Card USB Device (Disk drive) (Disk2)

When connected, I can access all the folders on the nuvi using Windows File Explorer.

I am unsure as to how to test transfer speeds from/to the nuvi.

I have had Garmin road and cycle sat navs for over 6 years now. Without exception every maps update have been a painfully slow process, it starts with a high speed but then it decreases considerably to what is now 656 Kb/s and over 60 %  to complete. I have used during the 6 years 3 different laptops, various networks, routers etc, it is definitely a Garmin issue, however when I contacted  them they sent a list of possible issues like something was wrong with my network, and although I have done everything they suggested the issue still persisted every time. Pity they treat customer in such way. 

The other sat nav the I use for work is a tom tom, I am not advertising as they all have their own faults, however not a single time I had issues downloading their maps.

Garmin, can you please treat your customers with respect and stop treating them like idiots suggesting all kind of possible problems with their computers when it is obviously an issue with your system. Many thanks 

Thanks again.

Garmin's USB cable I bear in mind (and use) is the one that came in the box with the device. I believe it's this item:

https://buy.garmin.com/en-GB/GB/p/pn/010-11478-01

(it has GARMIN logo embossed on the USB-A plug and it's 30 cm long)

Regarding peculiarity of these cables:

https://smallbusiness.chron.com/garmin-nuvi-wont-turn-its-plugged-64239.html

Garmin vs. Aftermarket

The factory-original Garmin USB cable has a 17.9 kilo-ohm resistor joining the fourth and fifth wires. Configured this way, the cable doubles the standard USB amperage and allows the Nuvi to draw up to 1 amp. That's enough power to charge and navigate at the same time. Many aftermarket cables will be wired for data only, or will produce just the standard 500 mA of USB current. A data cable will let you transfer information only between your Nuvi and a computer. A standard-amperage cable will charge your Nuvi but not power it.

Regarding the above supplied information... First of all, where in USB Treeview did you obtain it from exactly as I'm struggling to find the same page (========================== Summary =========================)?

UPDATED TO ADD: Got this, My USB TreeView version was rather dated!

In my case (selected information) when this device is selected on the left, that's what I can read on the right:

        ---------------- Connection Information ---------------
Connection Index         : 0x01 (1)
Connection Status        : 0x01 (DeviceConnected)
Current Config Value     : 0x01
Device Address           : 0x10 (16)
Is Hub                   : 0x00 (no)
Device Bus Speed         : 0x02 (High-Speed)
(...)

        --------------- Connection Information V2 -------------
Connection Index         : 0x01 (1)
Length                   : 0x10 (16 bytes)
SupportedUsbProtocols    : 0x03
 Usb110                  : 1 (yes)
 Usb200                  : 1 (yes)
 Usb300                  : 0 (no)
 ReservedMBZ             : 0x00
(...)

Also, matching the above:

      ========================== Summary =========================
Vendor ID                : 0x091E (Garmin International)
Product ID               : 0x47FB
USB Version              : 2.00
Port maximum Speed       : High-Speed
Device maximum Speed     : High-Speed
Device Connection Speed  : High-Speed
Self powered             : no
Demanded Current         : 500 mA
Used Endpoints           : 4

Please note that these items in your response:

USB Version              : 1.10

Device maximum Speed     : Full-Speed
Device Connection Speed  : Full-Speed

indicate that USB 1.10 instead of USB 2.0 protocol is in use - which is something that hinders upload speeds to device, and which indicate potential misconfiguration (cable/driver...)?

Also, can you show how your Device Manager presents your unit?

That's how it pans out in my case (matching what USB Treeview reports):

Lastly, assuming that you have some spare space on the device, you can copy some large file (1GB or similar) to/from the unit via Explorer and check the speeds you get in both directions.

In my case I'm getting steady ~15MB/s upload to and ~16 MB/s from the device (that's megabytes/s in both cases) - 1.5GB file I randomly grabbed has been moved both ways in around 1.5min. Which broadly matches what I witness when maps are pushed to the device (~14MB/s).

it starts with a high speed but then it decreases considerably to what is now 656 Kb/s and over 60 %  to complete.

Apologies, does that mean @60% of the overall process, or @40%?

I read it as the former, in which case both my earlier and later post would apply - please read and re-check.

We are making progress.

Thanks for sticking with this discussion Krzemien

Also, thanks for the heads up on the Garmin cable.  It turns out, I have two of them!  (no surprise, I have two units)

Yes, it would seem the Garmin cable has the added resistor.  This would allow the unit to be charged at the same time as it is operating.  As your notes stated, "A data cable will let you transfer information only between your Nuvi and a computer. A standard-amperage cable will charge your Nuvi but not power it".  This makes sense although it is also dependent on your USB port.  Some computers do limit the current to 500ma.

I do not believe my cable had any impact on my "slow map transfer" given the only difference between a standard cable is the added resistor, for the purpose of triggering a USB port to provide more juice.

As per your comment, the USB Version: 1.10 was when I had my nuvi 1350 connected.  When the DriveAssist 51 is connected, the USB Version: 2.00.  It is a little confusing keeping track when switching between the two devices.

Please note I was using my Drive Assist 51 when I attempted to download the maps from Garmin.  I have only used my nuvi to compare against your reports as you seem to have a nuvi model.  My unit is quite old and is very rarely used.  Any info regarding my nuvi is for reference only and should not cloud the issue of slow downloads to my DA51.

I am providing screen shots of similar USB TreeView

Data transfer tests:
transferring a 1GB file TO the Drive Assist 51 took 140 seconds at a sustained rate of 7MB/s
transferring a 1GB file FROM the Drive Assist 51 to the PC took 70 seconds at a sustained rate of 14MB/s

From these tests, I don't see any significant issue with with my configuration.

Any thoughts for next step?

Thanks again for detailed response.

With regards to the USB cable... it may (I say: may) have an impact on the quality of connection and its stability in that sense that if the unit you connect has depleted battery, unit may misbehave and lengthy update process might be a bit tricky. At least this is what I witnessed myself before.

Now, with the above in place and confirmed as working as expected, did you try to update maps again?

Also, do you see the same results (i.e. USB connectivity) for both units you own? Possibly worth connecting and disconnecting both with USB Treeview in place to confirm that USB 2 protocol is always in use (I would remain suspicious why did you get USB 1.1 only and investigate it a bit more - can't believe nuvi 1350 is USB 1.1 capable only).

you raise a valid point with respect to the USB cable and state of charge on the device.

I checked the battery on my DA51 and it was at 100%

I attempted to download (reinstall on the device) again (using a Garmin cable) and guess what?  Same SLOW data transfer.

Speed started at 6MB/s but started dropping after 40 seconds.

Data rate dropped to 1MB/s by 60 seconds, and down to 600kB/s at 90 seconds.

Then , I stopped the process.

I am only using my DA51 as I don't fully trust my old nuvi.  I don't use that device and do not want to mix results.

Thanks. So I'm clear when you say that you experience 'Same SLOW data transfer', what is the overall progress percentage showing in GE?

Is this - as I understand it - after 50% mark, when data (maps) is being pushed to device?

Also, what is USB Treeviewer telling (you can run it in parallel and see if any information in there changes)?